OptBand: optimization-based confidence bands for functions to characterize time-to-event distributions

Classical simultaneous confidence bands for survival functions (i.e., Hall–Wellner, equal precision, and empirical likelihood bands) are derived from transformations of the asymptotic Brownian nature of the Nelson–Aalen or Kaplan–Meier estimators. Due to the properties of Brownian motion, a theoretical derivation of the highest confidence density region cannot be obtained in closed form. Instead, we provide confidence bands derived from a related optimization problem with local time processes. These bands can be applied to the one-sample problem regarding both cumulative hazard and survival functions. In addition, we present a solution to the two-sample problem for testing differences in cumulative hazard functions. The finite sample performance of the proposed method is assessed by Monte Carlo simulation studies. The proposed bands are applied to clinical trial data to assess survival times for primary biliary cirrhosis patients treated with D-penicillamine.

     

Correlated linear models for the analysis of familial correlations

The problems of estimation and hypotheses testing on the parameters of two correlated linear models are discussed. Such models are known to have direct applications in epidemiologic research, particularly in the field of family studies. When the data are unbalanced, the maximum-likelihood estimation of the parameters is achieved by adopting a fairly simple numerical algorithm. The asymptotic variances and covariances of the estimators are derived, and the procedures are illustrated on arterial-blood-pressure data from the literature.     

Sampling properties of estimators of the log-logistic distribution with application to Canadian precipitation data

We consider the probability-weighted moment and the maximum-likelihood estimators of two parameters in the log-logistic distribution. Quantile estimators are obtained using both methods. The distributional properties of these estimators are studied in large samples, via asymptotic theory, and in small and moderate samples, via Monte Carlo simulation. The distribution is shown to be appropriate for a wide variety of meteorological data.     

Permissions and the social context

By focusing on formal intensive interview research, this essay explores how the sociohistorical context influences the routine procedures by which sociologists obtained permission to conduct their studies. We examine the permissions process within the specific historical context of the 1950s and contrast it with contemporary issues of informed consent. The need for a more theoretical and situational understanding of permissions is identified, both in regard to human—subjects regulations and social control. Her most recent books areMadwives: Schizophrenic Women in the 1950s (Rutgers University Press, 1987) andGender Issues in Field Research (Sage, 1988). She has written extensively in the fields of mental illness and social control. Her current research focuses on the sociological analysis of art and culture as well as the processes of doing and writing fieldwork. She is also the co-managing editor of theMid-American Review of Sociology.     

Comparison of two methods of measuring physical activity in South African older adults

The aim of this study was to assess the validity and reliability of the Yale Physical Activity Survey (YPAS) and the short version of the International Physical Activity Questionnaire (IPAQ) in older South African adults. The YPAS includes measures of weekly energy expenditure (EE) for housework, yard work, caregiving, exercise, and recreation. The IPAQ measures total time and EE during vigorous and moderate activity, walking, and sitting. The instruments were administered twice for test-retest reliability (men, n = 52, 68 +/- 5.4 years, and women, n = 70, 66 +/- 5.8 years). Data for criterion validity were obtained from accelerometers. YPAS reliability ranged from r = .44 to.80 for men and r = .59 to .99 for women (p < .0001). IPAQ reliability was lower for men (r = .29 to .76) than for women (r = .46 to .77). Criterion validity of the YPAS was .31 to .54 for men and .26 to .29 for women. The YPAS and short IPAQ had comparable results for reliability and criterion validity.     

Acceptance of Global Positioning System (GPS) Technology Among Dementia Clients and Family Caregivers

The purpose of this study was to examine the acceptance of Global Positioning System (GPS) used to help people with dementia, who are at risk for wandering in their communities. We used a mixed methods research approach that included use logs, pre and post paper-based questionnaires, and focus groups. Forty-five client-caregiver pairs (dyads) were included to use one of the GPS devices for an average of 5.8 months over a 1-year period. GPS acceptance was high; dyads were likely to continue using the GPS. According to the participants, the GPS provided caregivers peace of mind and reduced anxiety in dyads when clients got lost.     

A Comparison of Actual and Perceived Sexual Risk Among Older Adults

Sexual risk among older adults (OAs) is prevalent, though little is known about the accuracy of sexual risk perceptions. Thus, the aim was to determine the accuracy of sexual risk perceptions among OAs by examining concordance between self-reported sexual risk behaviors and perceived risk. Data on OAs aged 50 to 92 were collected via Amazon.com’s Mechanical Turk. Frequency of sexual risk behaviors (past six months) were reported along with perceived risk, namely, sexually transmitted infection (STI) susceptibility. Accuracy categories (accurate, underestimated, overestimated) were established based on dis/concordance between risk levels (low, moderate, high) and perceived risk (not susceptible, somewhat susceptible, very susceptible). Approximately half of the sample reported engaging in vaginal (49%) and/or oral sex (43%) without a condom in the past six months. However, approximately two-thirds of the sample indicated they were “not susceptible” to STIs. No relationship was found between risk behaviors and risk perceptions, and approximately half (48.1%) of OAs in the sample underestimated their risk. Accuracy was found to decrease as sexual risk level increased, with 93.1% of high-risk OAs underestimating their risk. Several sexual risk behaviors are prevalent among OAs, particularly men. However, perception of risk is often inaccurate and warrants attention.     

Gender and Women's Employment in the Male-dominated Profession of Dentistry: 1867–1917*

Cet article porte sur les expériences des femmes qui ont pratiqué la dentisterie - profession dominée par les hommes - en Ontario entre 1867 et 1917. L'auteure examine l'entrée des femmes dans cette profession et leurs expériences quant à la formation et à la pratique. La situation des femmes qui entraient en dentisterie et de celles qui optaient pour la médecine était différente: les femmes n'ont jamais été exclues de la profession dentaire. Tant en médecine qu'en dentisterie, une fois dans la pratique professionnelle les femmes étaient marginalisées et incitées à adopter des comportements et des rôles propres à leur sexe. This paper explores women's experiences in the male-dominated profession of dentistry in Ontario between 1867 and 1917. It examines the entrance of women into the dental profession, and their experiences in dental education and dental practice. Circumstances surrounding women's entrance into dentistry were different from those surrounding the entrance of women into medicine: women were never excluded from the dental profession. Nevertheless, once in professional practice, women in the two professions shared experiences of marginalization and of encouragement to pursue sex-typed behaviour and roles.     

Bruce A. Seaman and Dennis R. Young: Handbook of Research on Nonprofit Economics and Management

VOLUNTAS: International Journal of Voluntary and Nonprofit Organizations -